Photoconductography employing spongy images containing gelatin hardeners



Oct. 8, 1963 D. R. EASTMAN ETAL 3,106,517

PHOTOCONDUCTOGRAPHY EMPLOYING SPONGY IMAGES CONTAINING GELATIN HARDENERS Filed July 28, 1960 I Fig./ i /2 d GELAT/N 30 spa/var HARM/YER 32 I 4 25 3/ 35 3/ W? L Pi J' 32 Fig. 2

DONALD R. EASTMAN RAYMOND F RE/THEL INVENTORS ATTORNEYS United States Patent r 3,106,517 PHOTOCGNDUCTOGRAPHY E M P L 0 Y I N G SPONGY WAGES CONTAINING GELATIN HARDENERS Donald R. Eastman and Raymond F. Reithel, Rochester,

N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey Filed July 28, 1960, Ser. No. 45,952 9 Claims. (Cl. 204-118) This invention relates to photoconductography.

Photoconductography forms a complete image at one time or at least a non-uniform part of an image as distinguished from facsimile which at any one time produces only a uniform dot. The present invention would be useful with facsimile but finds its greatest utility in photoconductography.

Cross reference is made to the following series of cofiled applications:

Serial No. 45,940, John W. Castle, In, Photoconductography Employing Reducing Agents.

Serial No. 45,941, now abandoned, Raymond F. R-eithel, Photoconductolithography Employing Nickel Salts, continuation-impart Serial No. 120,863, filed June 7, 1961.

Serial No. 45,942, Raymond F. Reithel, Photoconductolithography Employing Magnesium Salts (now Fatent No. 3,053,179).

Serial No. 45,943, now abandoned, Raymond F. Reithel, Photoconductography Employing Spongy Hydroxide Images, continuation-impart Serial No. 120,035, filed June 27, 1961.

Serial No. 45,944, Raymond F. Reithe-l, Method for Making Transfer Prints Using a Photoconducto-graphic Process.

Serial No. 45,945, Raymond F. Reithel, Photoconductography Employing Manganese Compounds.

Serial No. 45,946, now abandoned, Raymond F. Reithel, Photoconductography Employing Molybdenum or Ferrous Oxide, continuation-in-part Serial No. 120,036, filed June 27, 1961.

Serial No. 45,947, now abandoned, Raymond F. Reithel, Photoconductography Employing Cobaltous or Nickelous Hydroxide, continuation-impart Serial No. 120,037, filed June 27, 1961 (now Patent No. 3,057,788).

Serial No. 45,948, Donald R. Eastman, Electrophotolithography.

Serial No. 45,949, Donald R. Eastman, Photoconductolithography Employing Hydrophobic Images.

Serial No. 45,950, Donald R. Eastman and Raymond F. Reithel, Photoconductogra-phy Employing Electrolytic Images to Harden or Soften Films.

Serial No. 45,951, now abandoned, Donald R. Eastman and Raymond F. Reithel, Photoconductography Employing Absorbed Metal Ions, continuationdn-part Serial No. 120,038, filed June 27, 1961.

Serial No. 45,953, John J. Sagura, Photoconductography Employing Alkaline Dye Formation (now Patent No. 3,057,787).

Serial No. 45,954, John J. Sagura and James A. Van Allan, Photoconductography Employing Quaternary Salts.

Serial No. 45,955, Franz Urbach and Nelson R. Nail, Uniform Photoconductographic Recording on Flexible Sheets.

Serial No. 45,956, Franz Urbach and Nelson R. Nail, High Contrast Photoconductographic Recording.

Serial No. 45,957, Nicholas L. Weeks, Photoconductography Involving Transfer of Gelatin.

Serial No. 45,958, Donald R. Eastman, Photoconductolithograph Employing Rubeanates.

Serial No. 45,959, Donald R. Eastman and Raymond F. Reithel, Electrolytic Recording with Organic Polymers.

Serial No. 46,034, Franz Urbach and Donald Pearlman, Electrolytic Recording.

Electrolytic facsimile systems are well known. Electrolytic photoconductography is also known and is described in detail in British 188,030, Von Bronk, and British 464,112, Goldmann, modifications being described in British 789,309, Berchtold, and Belgium 561,403, Johnson et al.

The present invention is closely related to our cofiled application Serial No. 45,950 listed above entitled Photoconductography Employing Electrolytic Images to Harden or So-ften Films.

S'mce it involves hardening or softening of gelatin and/or organic polymers it is also related to the above listed co-filed applications by East-man and Reithel entitled Electrolytic Recording With Organic Polymers and by Unbach and Pearlman entitled Electrolytic Recording. It differs from the cofiled application of Sagura having to do with Alkaline Dye Forms in that it relates to hardening and softening of separate sheet materials.

In the present invention the gelatin may adhere to the non-image areas and form a gelatin relief on the photoconductor.

Since this invention may be practiced with either gelatin or water-permeable polymer layers, the term waterpermeable, film forming layer will be used to denote all such layers. Also the invention encompasses both hardening and softening of gelatin and hardening and softening polymer layers, although it is most versatile when used to harden gelatin.

In the present invention the photoconductographic image is used to control the solubility of gelatin or of certain polymers coated on a separate sheet. The object of the invention in this connection is to provide a process which yields prints of better contrast than are obtained when the final image is formed directly on the photoconductive layer by electrolytic deposition from an electrolyte useful in photoconductography. Also the recording layer itself carrying the gelatin or polymer need not be electrically conducting.

Other objects of the invention depend on how the hard ened or softened layer is utilized. The object of the invention thus is to provide a photoconductographic process which produces any one of the following results:

A. Single copy B. Lithographic master C. Spinit master D. Stencil master E. Colloid transfer master (bearing an operational similarity to that described in US. Patent 2,596,756)

F. Dye irnbibition master G. Magnetic printing master H. Ion transfer master gel solutions are relatively insoluble in aqueous media above this critical pH value. STAM is the ammonium salt of styrene maleamic acid copolyrner and STAM and gelatin dissolved in water constitute a STAM-gel solution.

Gelatin softening (slubiIizati0n).-It is also well known that aqueous solutions of certain inorganic chemicals, e.g. potassium alum (K Al (SO .24H O) are effective hardening agents of lime-processed gelatin only within a narrow pH range (pH between 3-6). Within this range, the melting point of gel layers, so hardened, is much higher than at lower or higher pH values. Raising the pH softens gelatin which has been so hardened. Unhardened lime-processed gelatin layers also show a marked dependence of melting point on pH but the differential is not nearly as pronounced as with potassium alum hardened gels.

Gelatin, as it well known, may also be softened, or tenderized, by the action of certain proteolytic enzymes. One such material is marketed commercially by the Takamine Corporation.

Synthetic polymer soIubilizati0n.Dry layers of certain synthetic organic polymers of the general class represented by cellulose acetate phthalate, poly methyl methacryla-te co-methacrylic acid, or poly styrene co-maleamic acid are insoluble in acidic aqueous solutions, but can be rendered soluble in alkaline media.

Synthetic polymer ins0lubilizazi0n.-Layers of other organic polymers of the class represented by polyvinyl pyridine, are soluble in aqueous acid media but insoluble in alkaline media. Coated from acid water solutions, these layers can be insolubilized by contact with alkaline solutions.

The visibility or lack of visibility of the electro-de posited material (i.e. the image) on the photoconductive surface is irrelevant to the practice of this invention.

This invention is essentially a two-step process in which the first step is electrolytic and the second chemical. With various subsequent treatments, such as washoff, this second chemical step produces (1) a physical change, (2) a differential in mechanical or thermo-mechanical properties, (3) a differential in dye absorptivity, and/ or (4) a differential in receptivity to greasy lithographic inks, when wetted with the proper press fouutain solutions.

Specifically, this invention consists of the imagewise electrolyitc deposition, on a photoconductive surface, of an image, a spongy absorbent material (a spongy image) which either (a) during electrolytic deposition (which is the preferred method of operation) or (b) in a subsequent step after electrolysis, abs-orbs (or adsorbs) chemical agents. These chemical agents are transferred into specially coated separate recording layers to either (a) harden gelatin, (,8) soften (solubilize) gelatin, (7) insolubilize organic polymers, or (6) solubilize organic polymers.

The electrolytic deposit obtained from aqueous solutions of magnesium salts which consists of the metal hydroxide (or hydrated oxide) has been found to be particularly useful for the practice of this invention because of its spongy, absorbent properties, its resistance to destruction by other necessary chemical agents, and its alkaline properties.

The hydrous electrolytic deposits obtained from aluminum, cobalt, chromium, iron, manganese, nickel, and cerium salts can also be utilized for the practice of this invention.

The invention will be fully understood from the examples given below and from the following description when read in connection with the following drawings in which:

FIG. 1 is a schematic flow chart illustrating a preferred embodiment of the invention.

FIG. 2 similarly illustrates an alternative to one step of the process shown in FIG. 1.

FIGS. 3, 4 and illustrate various printing processes utilizing the gelatin relief which results from the present invention as shown in FIG. 1.

In FIG. 1 a transparency 10 is illuminated by a lamp 11 and image thereof is focused by a lens 12 on a photo conductive zinc oxide in resin layer 15 carried on a conducting support 16. The transparency is moved to the left as indicated by the arrow 17 and the photoconductor, as indicated by the arrow 18, moves synchronously with the image of the transparency 10.

While the photoconductivity image persists in the zinc oxide layer 15, it is passed under a brush 29 containing an electrolyte. A potential difference is maintained between the brush 20 and the roller 21 by a source of potential indicated schematically at 22. The zinc oxide layer is the cathode as shown, but A.C. potential may be applied since the zinc oxide in contact with the electrolyte acts as a rectifier so that it is a cathode in the electrolytic action. The electrolyte contains magnesium or any of the other metal ions which form spongy images as described in the cofiled applications. A spongy image 23 is deposited on the exposed areas of the photoconductor 15. Then according to the invention, this image is treated with a gelatin hardener (or in other embodiments a gelatin solubilizer of a polymer hardener or softener). The treatment is applied by a brush 24 and the spongy image 25 containing the hardener is pressed into contact with a gelatin or polymer layer 30 carried on a suitable support 31, pressure being applied by rollers 32.. The layer 30 is such that it is hardened or softened by the material in blush 24, and hence in the image 25. In the case where it is hardened, or insolubilized, a supply of water 37 washes off the relatively soft or soluble areas and leaves a relief image 35 on the support 31.

Alternatively, as shown in FIG. 2, when the layer 30 is a hardened one, softened by the magnesium hydroxide image 23, the spray of water 37 washes off the areas thus softened and leaves a relief image 38 on the support 31. Either of these relief images resulting from FIG. 1 or FIG. 2 may be used in any of the subsequent reproduction processes. For simplicity, the relief image 35 is the one illustrated in FIGS. 3, 4 and 5.

In FIG. 3 the relief image is used for imbibition printing. An imbibition dye 41 is applied by a roller 40 to the relief image 35, for example an image of gelatin. This relief image is then pressed into a receiving sheet 43 and the dye transfers as indicated at 44. This FIG. 3 could also illustrate the use of the relief image as a spirit transfer master. In this case the dye is applied to the relief or is included in the original gelatin layer, and in the presence of alcohol a small portion of dye transfers to the receiving sheet. Similarly FIG. 3 could represent the application of magnetic material to the relief for subsequent use in magnetic printing.

The sheet 31 may be either hydrophilic or hydrophobic and the image 35 may be hydrophobic or hydrophilic. In the arrangement shown the support 31 is a hydrophobic sheet and the image 35 is gelatin which is hydrophilic even when hardened with formaldehyde. In FIG. 4, this layer of gelatin is moistened by a roller 50 which applies a standard fountain solution 51. The plate is then inked with a standard litho greasy ink 53 by a roller 52, the ink adhering as shown at 54 to the areas of the support 31 which are not covered by the image 35. In the usual offset method this ink is transferred to an offset drum 57 as indicated at 58 and is printed on a succession of sheets of paper such as shown at 59.

An alternative lithoprinting system which has proven most satisfactory utilizes the standard litho materials (e.g. Duplimat) supplied with office type litho presses, particularly for use with colloid transfer processes. These standard sheets will accept and hold soft gelatin, which is hardened and rendered hydrophobic. The sheet is then treated with a solution which renders the support hydrophilic, for standard lithoprinting on an ofiice litho printer such as supplied by the Addressograph Multigraph Corporation.

In the present invention, this Duplimat material is utilized with differentially hardened gelatin made as shown schematically in FIG. 5. The differentially hardened gelatin layer with hardened areas 34 (corresponding to the relief areas 38 of FIG. 2) and with unhardened areas 33 is pressed in contact with a hydrophobic litho (Duplimat) master 61, pressure being applied by rollers 60. Part of the unhardened gelatin 33 transfers as shown at 63 to the support 61. This image is treated by swabbing with a brush 64 which applies a gelatin hardener, tannic acid, to harden the transfer image 63. The hardening in this case is sufiicient to make the gelatin hydrophobic. The whole sheet is then treated with a solution in a brush 65 which is the standard solution (Platex) supplied with the sheet "61 to render the surface 62 thereof hydrophilic but leaving the hardened gelatin layer 63 hydrophobic. The support 61 with the hydrophilic areas 62 and the hydrophobic areas 63 is now ready for lithoprinting on a standard press, the operation being schematically shown in FIG. 5. The moistening roller 50 applies a fountain solution 51 which wets the area 62. The inking roller 53 then applies a greasy ink to the image areas 63, the ink adhering to these areas as indicated at 70. Then in the usual way, the ink 70 transfers to an oifset drum 71 as indicated at 72 and prints onto a sheet of paper 73 passed in contact with the drum 71.

The gelatin relief made in accordance with the present invention may be transferred to a silk screen to act as a stencil for silk screen printing.

Examples of uses of solubility images are as follows:

Gelatin hardening.-Since organic hardening agents such as formaldehyde, or p-quinone do not form useful electrolytic deposits (in cathodic operation) on ZnO photoconductive surfaces, it is necessary either (1) to apply these hardening agents to an absorbent imagewise deposit or (2) to co-deposit the hardening agent with a hydrous oxide forming material. The hardening rate and efiiciency of these organic agents increases with increased alkalinity. This alkalinity can be supplied in either or both of two ways, (1) by the alkalinity of the image deposit and/ or (2) by adjusting the pH of the gelatin before coating.

Most of the inorganic hardening agents, e.g. potassium alum, chrome alum, cerium salts, etc. which do form hydrous electrolytic deposits from aqueous solutions of their soluble salts .do not require the inclusion of other hydroxide-forming metal salts in the electrolytic developer. However, the deposition of the hydroxide of iron, for example, is improved by the inclusion of magnesium or manganese salts in the developer.

When the hardening agent (e.g. STAM, or cobalt salts) is ineffective in acid media, the dry layers coated from acid gel solutions containing these agents can be insolubilized by contact with alkaline reactive electrolytic deposits, e.g. Mg(OH) Any pigments, dyes, or other materials used in the process must not detrimentally soften or harden the gelatin or polymer or adversely affect its other properties.

The following ten systems represent preferred uses of hardened gelatin relief images.

(1) Single copy wash-0ff.-An imagewise distribution of deposited hardening agent or hydroxyl ions from an alkaline deposit is transferred by pressure contact, into a pigmented or dyed gelatin layer coated on a separate support. The unhardened gelatin is removed by washing in hot water. The resultant print is a positive if the exposure was made to a negative original.. With certain gelatin layers, parts of the soft gelatin adheres to the Zinc oxide layer in the non-image bearing areas to produce a direct positive image on the zinc oxide surface; this is a useful added feature.

(2) Single copy thermo-mechanical transfer.An imagewise distribution of hardening agent, or hydroxyl ion from an alkaline deposit, is transferred, by pressure contact, into a pigmented or dyed gelatin layer on a separate substrate. The unhardened gel is then transferred by thermo-mechanical means onto a separate receiving sheet. If the photoconductor is exposed to a positive original, the remaining unhardened gel on the separate recording layer will be a negative copy, and the transferred gel on the receiving sheet a positive copy.

(3) Lithographic printing recording layer as master (wash-ofi).Gelatin hardened with formaldehyde repels greasy lithographic inks. With the gel recording layer on an ink-receptive substrate, a positive-to-positive lithographic printing master can be produced.

(4) Transfer to Duplimat.-The unhardened gelatin is transferred, by pressure contact, onto the surface of a gelatin-receptive Multilith Type sheet and the gelatin image rendered ink-receptive by chemical treatment (described in connection with FIG. 5 above). This provides a direct positive system.

(5) Spirit duplicatinglf spirit soluble dyes are incorporated in the separate recording layer, the masters or prints obtained by method (1) or (2) will provide a suitable duplicating master for this system.

(6) Stencil duplicating.A gelatin impregnated silk screen or tea-bag paper (or any suitable open-mesh material) is contacted with a hardening-agent image-deposit. The unhardened gel areas are then removed by a wash-off step. This provides a direct-positive system.

(7) Colloid transfer master.-The unhardened (dyed or pigmented) gelatin is transferred from the separate recording layer, by pressure-contact onto a seriesof suitable receiving sheets. A few copies can be obtained from a single master. This provides a positive-to-positive system.

(8) Dye imbibition printing.The gelatin image obtained either after wash-off or by transfer to a separate receiving sheet, will absorb dyes. As is common in dye transfer processes, these dyes can be transferred onto a separate receiving sheet.

(9) Magnetic printing.Magnetic printing masters, negative-to-positive method or positive-to-positive, depending on which of the above processes is used in making the relief, can be produced by incorporating magnetically hard materials in the recording layer.

(10) Jon transfer printing.Color-forming agents incorporated in the gelatin can be transferred, by use of a suitable solvent, into another layer containing other agents and upon chemical reaction form a visible image.

Gelatin softening (s0lzibilizati0n).For example, gelatin layers hardened with potassium alum can be solubilized, by contacting them with an alkaline image deposit, by virtue of the strong dependency of hardening efficiency upon pH. Such embodiments are particularly useful in the following two examples.

(1) Single copy wash-ofi.-Wash-off of the softened (solubilized) areas provides a direct-positive copying system.

(2) Single copy transfer of softened gelatin-Transfer of the softened gel to a separate receiving sheet will provide a negative-to-positive process.

Polymer s0lnbilizati0n.-The dry layers of these alkaline soluble polymers, coated from organic solvent solution, can be solubilized by contact with alkaline reacting image deposits. Even better results are obtained in this process if hydrophilic (wettable) pigments are used in the layer. This aids in obtaining the maximum degree of image-material transfer and penetration. Examples which have proven particularly usable to this embodiment of the invention are as follows (four examples).

(1) Single c0py.Hydroxyl ions from an alkaline image deposit are transferred, by pressure contact, into the dyed, or pigmented layer. The solubilized areas are then removed by washoif. This furnishes a direct-positive copying process.

(2) Lithographic printing.When wetted with lithographic wet-out solutions, the areas contacted by the alkaline image deposit will repel greasy lithographic inks. The remaining areas are ink-receptive. This provides a direct-positive copying process.

(3) Stencil duplicating.A silk screen or tea-bag impregnated with one of these polymers is contacted with an alkaline image deposit, and the solubilized areas washed out. This provides a negative-to-positive copying process.

(4) Magnetic prz'ntilzg.-lncorporation of hard magnetic materials in the polymer layers will provide a positive-to-positive system for producing a magnetic printing master.

The following specific examples of the various embodiments of the invention were all carried out with photoconductive layers which consisted of dye sensitized zinc oxide dispersed in a resin binder coated on an aluminum foil, paper, laminate support using electrolytic development which utilizes the persistency of photoconductivity exhibited by these layers. The invention can, of course, also be carried out in photoconductive processes involving simultaneous exposure and development. In all of the examples, the electrolysis was carried out with aluminum foil backing of the photoconductive layer held at a negative potential with respect to the counter electrode and the electrolytic developer was carried in a viscous sponge brush-type counter electrode.

Example 1 A gelatin recording layer was prepared as follows:

6 g. Grasol Fast Black 6" (Geigy dyestufi) 100 cc. of 2% gelatin-lime processed 6 cc. ethyl alcohol Ball mill for 18 hours in a pint-sized mill with 12 borundum balls. Filter through a balloon silk filter bag. To 50 cc. of the above mixture was added:

50 cc. of 10% gelatin 0.4 g. KNO 1.5 cc. glycerol Filter through a balloon silk filter bag and coat 0.005 inch thick on electron-bombarded, titanox pigmented polyethylene treated paper stock.

Magnesimn-forma1dehyde.-As one example of this invention, a dye-sensitized zinc oxide layer was exposed for seconds to 400 ft. candle tungsten illumination through a 0.3 density increment photographic step-wedge. The resulting conducting image was developed electrolytically using a 1% magnesium nitrate hexahydrate plus 4% formaldehyde solution contained in a viscose sponge brush electrode, held at 70 volts, positive with respect to the zinc oxide layer with ten strokes development. The excess electrolyte was removed from the zinc oxide surface with an absorbent tissue. A sheet of the above prepared gelatin coating 0.005 inch wet thickness was moistened with cold tap water and rolled into contact with the zinc oxide layer containing the magnesium hydroxideformaldehyde hardening image. After allowing 50 seconds for transfer of formaldehyde and hardening to ocour, the gelatin layer was peeled from the zinc oxide surface and the soft gelatin was removed by a hot water rinse (140 F.). A hardened gelatin plus dye pigment relief image remained on the polyethylene coated sheet. A step-wedge image of soft gelatin remained on the zinc oxide layer in a pattern corresponding to areas of low exposure. The hardened gelatin step-wedge image indicated that an exposure of 125 ft.-candle-seconds was required on the zinc oxide layer to produce hardening of the gelatin from a photoconductographic image produced as above. This example is also included in our cofiled application on the use of electrolytic images to harden or soften films. -It is included here because the formaldehyde may be carried by the spongy Mg(OH) image.

For use in Examples 2, 3 and 4, gelatin layers were prepared in the following manner:

6.0 g. Grasol Fast Black G 100 cc. 2% gelatin 2 cc. ethyl alcohol 8 This solution was ball milled for 67 hours in a pint-sized mill using 12 borundum balls and to it was added:

cc. 10% gelatin 20 cc. distilled water The solution was filtered through a balloon silk filter bag and coated at pH=6.5, pH=4.9, and pH=4.0 on polyethylene coated paper stock, 0.003 inch and 0.005 inch wet thickness.

Example 2 Magnesium-p-quinone.-A dye-sensitized zinc oxide layer was exposed for 3 seconds to 400 ft. candle tungsten illumination through a high-contrast line negative. The conducting image was developed electrolytically using a 1% magnesium nitrate hexahydrate solution held in a vis cose sponge brush electrode 70 volts positive with respect to the zinc oxide layer. The excess electrolyte was removed from the zinc oxide surface with an absorbent tissue. The absorbent magnesium hydroxide image was bathed with a 2% solution of p-quinone. The excess p-quinone was removed with an absorbent tissue and a sheet of the above gelatin coating (0.005 inch at pH=6.5) was moistened with cold tap water and rolled into contact with the above prepared image. After allowing 50 seconds for the transfer of p-quinone and image hardening to occur, the sheets were separated by peeling and the soft gelatin was removed by rinsing in 120 'F. tap water for 10 seconds. A hardened gelatin relief image remained on the polyethylene coated paper support.

Example 3 Magnesium-gold.-A sheet of dye-sensitized zinc oxide was exposed and developed as in Example 2 to produce a spongy absorbent magnesium hydroxide image. This image was then bathed with a 1% solution of aurochloric acid and the excess removed with an absorbent tissue. A sheet of gelatin coating prepared as described above (pH=6.5) was moistened with cold tap water and rolled into contact with the above prepared image. After 60 seconds tnansfer time, the sheets were separated and an additional 2 minutes hardening time was allowed before the soft gelatin was removed in F. tap water.

Example 4 Manganese-irom-A sheet of dye-sensitized zinc oxide was exposed and developed as in Example 2 using a solution of 0.75% ferrous sulfate heptahydrate plus 0.5% manganous nitrate. Transfer was effected as in Example 2 using the gelatin layer coated .005 inch wet thickness with pH=4.0. After peeling the layers apart, 2 minutes were allowed for additional hardening before the soft gelatin was removed by rinsing in F. tap water. Since it is possible that the iron is only held by the spongy manganese hydroxide image and is not deposited electrolytically, this example is included her as well as in my cofiled application on the use of electrolytic images to harden or soften films.

Example 5 Lithographic printing-recording layer as master.-The gelatin layer was prepared as follows:

10 g. Fe O 100 cc. 2% gelatin 2 cc. ethyl alcohol The mixture was ball milled for 42 hours in a pint-sized mill with 12 borundum balls. Then 100 cc. 10% gelatin was added and the mixture was filtered through a balloon silk filter bag and coated 0.005 inch thick on polyethylene coated paper stock.

A dye-sensitized zinc oxide layer was exposed for 3 seconds to 400 ft.-candle tungsten illumination through a positive line transparency and developed electrolytically as in Example 1. A sheet of the above gelatin coated paper was moistened and rolled into contact with the electrolytically produced magnesium hydroxide-formaldehyde image material. After allowing 50 seconds for formaldehyde transfer and hardening to occur, the sheets were separated by peeling. The soft gelatin was rinsed out of the image areas with 120 F. tap water revealing the hydrophobic polyethylene sheet. The wetted formalin hardened gelatin in the background was ink repellent. The sheet was force air dried and mounted on a Multilith, Duplimat master and treated with Repelex Fountain Solution 1:32 dilution and run on a Multilith No. 500 press using Van Son Black No. 40904 ink. One hundred copies were made from the master.

Example 6 Image transfer to M alzilitlz-type gelatin receiving master.--The gelatin transfer matrix was prepared in the following manner:

12 g. Grasol Fast Black G 100 cc. 2% gelatin 4 cc. ethyl alcohol Ball mill for 5 hours in a pint-sized ball mill using 12 borundum balls. Add 100 cc. of 20% gelatin.

Filter through a balloon silk filter bag and coat 0.005 of an inch on polyethylene coated paper stock.

A dye-sensitized zinc oxide layer was exposed and developed as in Example 2. A hardened gelatin image was produced on a sheet of the above coated gelatin layer as in Example 2. The sheets were separated by peeling and the soft gelatin in the image areas (the background was hardened) was transferred by pressure rollers to a gelatin receiving Multilith-type master. This transferred image gelatin was then rendered ink receptive by bathing it with a solution of Multilith Image Hardening Solution for Verifax Method. The background areas of the master were then rendered hydrophilic with Platex solution and the master was run on a Multilith No. 500 lithograph press using Van Son Black No. 40904 Lithographic Ink. One hundred copies were made from the master prepared in this manner.

Example 7 Spirit Master.-The gelatin plus spirit-soluble-dye recording layer was prepared as follows:

50 cc. of 5% gelatin 0.1 g. methyl violet 0.05 g. saponin The solution was filtered through a balloon silk filter bag and coated 0.005 and 0.010 inch thick on polyethylene coated paper stock. A sheet of dye-sensitized zinc oxide was exposed for 3 seconds to 400 ft. candle tungsten illumination through a high-contrast line negative. The image was developed electrolytically as in Example 1. A sheet of the above recording layer was moistened with tap water and rolled into contact with the zinc oxide layer containing the hardening image. Fifty seconds was allowed for transfer and hardening to occur. The gelatin layer was peeled from the zinc oxide surface and the soft gelatin was removed by a S-second rinse in 130 F. tap water, and then was dried. A sheet of Ditto brand receiving paper was moistened with alcohol-NaOl-I mixture and rolled into contact with the gelatin plus dye image prepared above. Five seconds were allowed for transfer of dye and the receiving paper was removed. This was repeated with a second sheet etc. Ten copies were made to illustrate the multiple copy process.

Example 8 Colloid transfer master.-The gelatin transfer matrix was prepared as follows:

12.0 Grasol Fast Black G 100 cc. 2% gelatin 4 cc. Ethyl alcohol The solution was ball milled for 5 hours in a pint-sized mill with 12 borundum balls and was filtered through a 10 balloon silk filter bag. Then was added cc. of 20% gelatin. This solution was filtered again and coated 0.010 inch thick on polyethylene coated paper stock.

A dye-sensitized zinc oxide layer was exposed for 3 seconds "to 400 ft. candle tungsten illumination through a positive transparency line copy. The conducting image was developed electrolytically using a solution of 1% magnesium nitrate hexahydrate plus 4% formaldehyde at pH=8.5 with sodium hydroxide as in Example 1. A sheet of the above prepared gelatin layer was moistened with cold tap water and rolled into contact with the above prepared image material. After allowing 50 seconds for formaldehyde transfer and hardening of the gelatin, the layers were separated by peeling and parts of the soft gelatin were transferred to Verifax Copy Paper (92002) by pressure rollers and peeling. Ten copies were made from this one master.

Example 9 Thermo-mechanical stripping.-The gelatin transfer matrix was prepared as follows:

15 g. F6304 (ferromagnetic) 100 cc. 2% gelatin The mixture was ball milled for 52 hours in pint-sized mill with borundum balls. Then 1 g. Uni-Aga dispersed in 80 cc. distilled water at 75 C., 20 cc. 10% gelatin and 2 cc. wetting agent were added hyde transfer and hardening to occur, the sheets were separated by peeling. The gelatin coated polyethylene sheet containing the image hardened gelatin was run through heated rollers at approximately F. in contact with a sheet of Verifax Copy Paper. The sheets were separated by peeling and there was complete transfer of the soft gelatin to the Verifax Copy Paper to produce a positive reproduction, the hardened gelatin remaining on the polyethylene coated sheet in the form of a negative reproduction. If exposure is made through a negative transparency, the useful positive image remains on the polyethylene coated sheet and the soft background gelatin transfers to the Verifax receiving sheet to produce a negative.

Example 10 Magnetic printing marten-The gelatin plus ferromagnetic pigmented recording layer was prepared in the following manner:

50 cc.-of 2% gelatin (lime processed cattle-hide) 3.0 g. Fe O (ferromagnetic) 2 cc. ethyl alcohol These compounds were mixed together in a pint-sized ball mill with 12 borundum balls and milled for 18 hours. To the above mixture was added:

50 cc. of 10% gelatin 0.4 g. KNO 0.5 g. Uni-Aga (from gelled concentrate) at 50 C.

The mixture was filtered through a balloon silk filter bag and coated 0.005 inch thick on polyethylene treated paper stock.

The process for producing a relief image here was the same as for Example 1 except that the exposure was made through a high-contrast line copy negative transparency. The image (consisting of hardened gelatin plus 1 l Fe O was air dried and was magnetized by running one pole face of a bar magnet across the surface of the image material several times. The print Was then bathed in a suspension of carbonyl iron in cyclohexane for 10 seconds. The print was allowed to dry and the carbonyl iron particles held by the magnetic image were transferred between pressure rollers to a specially treated pressure transfer paper. A carbonyl iron positive image resulted.

Example 11 Gelatin sofenting (single copy wash-0fl).-A sheet of the dyed gelatin material prepared for use in Examples 2, 3 and 4 (pH=4.9) was bathed for 60 seconds, with agitation, in 100 cc. of a 1%, by Weight, solution of chromic chloride hexahydrate, was rinsed briefly with distilled water, and then was air dried at room temperature for several hours before use. This constitutes the recording layer.

A sheet of dye sensitized zinc oxide material was exposed for 5 seconds to 500 ft. candles tungsten radiation incident upon a high contrast line copy positive transparency in contact with the photoconductive surface and then was developed electrolytically at 60 volts with a viscose sponge wetted with an aqueous solution containing 1% by weight, magnesium nitrate hexahydrate, the pH of which was adjusted to 9.0 with 2% sodium hydroxide solution.

After electrolytic development, the print surface was dried by blotting with an absorbent tissue which removed the excess electrolyte from the non-image-bearing areas. An aqueous solution containing 0.05%, by weight, of a proteolytic enzyme (Takamine Corp.) was applied to the photocon surface bearing the Mg(OH) image deposit. and the excess was removed by blotting with an absorbent tissue.

The water-moistened surface of the gel recording layer described above was then rolled into contact with the image-bearing photocon surface.

After 15 minutes, the recording layer was peeled off and the softened gel areas, corresponding to the areas bearing the absorbed enzyme material were removed by washing in hot Water. The gel corresponding to the areas without image deposit was unaffected by this treatment. Exposure of the zinc oxide layer to a positive original resulted in a positive print on the recording layer.

Having described various examples of our invention, it is pointed out that the invention is not limited thereto, but is of the scope of the appended claims.

We claim:

1. In a photoconductographic process in which an image pattern of variations in electrical conductivity is produced in a photoconductive layer, the steps of electrolytically cathodically depositing a spongy image, applying a gelatin hardening agent to said image to be absorbed thereby and placing in contact with the image a layer of gelatin hardenable by said agent carried on a support.

2. The process according to claim 1 in which said applying is subsequent to said depositing and said hardening agent is selected from the group consisting of paraquinone, aurochloric acid, cerous ions, iron ions and formaldehyde.

3. The process according to claim 1 in which said agent is in the electrolyte so that said applying is simultaneous with said depositing and said hardening agent is selected from the group consisting of cerous ions, iron ions and formaldehyde.

4. In a photoconductographic process in which an image pattern of variations in electrical conductivity is produced in a photoconductive layer the steps of electrolytically cathodically depositing a spongy image, applying a proteolytic enzyme, gelatin tenderizing, agent to said image to be absorbed thereby and placing in contact with the image a layer of gelatin softenable by said agent carried on a support, whereby the gelatin is softened by said image.

5. The process according to claim 4 in which part of the gelatin adheres to the spongy image and forms a gelatin relief on the photoconductor.

6. In a photoconductographic process in which an image pattern of variations in electrical conductivity is produced in a photoconductive layer, the steps of electrolytically cathodically depositing a spongy image, applying to said spongy image an agent capable of changing the solubility in Water of a water-permeable film forming layer to be absorbed by said spongy image, and placing in contact with the spongy image, carrying said agent, a Water-permeable, film forming layer of material Whose solubility in water is changeable by Said agent carried on a support.

7. A matrix for patternwise hardening a gelatin layer by contact therewith, comprising a support, a photoconductive layer on the support, a spongy metallic hydroxide image pattern on said layer, and a gelatin hardening agent absorbed into said spongy pattern, said agent being selected from the group consisting of paraquinone, aurochloric acid, cerous ions, iron ions and formaldehyde.

8. A matrix for patternwise softening a gelatin layer by contact therewith, comprising a support, a photoconductive layer on the support, a spongy metallic hydroxide image pattern on said layer, and a proteolytic enzyme, gelatin tenderizing, agent absorbed into said spongy pattern.

9. A matrix for patternwise changing the solubility in water of an organic polymer layer by contact therewith, comprising a support, a photoconductive layer on the support, a spongy metallic hydroxide image pattern on said layer, and an agent capable of said changing absorbed into said spongy pattern.

References Cited in the file of this patent UNITED STATES PATENTS 571,531 Langhans Nov. 17, 1896 2,393,378 Johoda et al. Jan. 22, 1946 2,763,553 Clark et al. Sept. 8, 1956 FOREIGN PATENTS 215,754 Australia June 23, 1958 'UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 106,517 October 8, 1963 Donald R. Eastman et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 13, for "it" read is column 4, line 21, for "of" read or column 8, line 56, for "her" read here Signed and sealed this 14th day of April 1964.

(SEAL) Attest: EDWARD J. BRENNER ERNEST W., SWIDER Attesting Officer Commissioner of Patents 

1. IN A PHOTOCONDUCTOGRAPHIC PROCESS IN WHICH AN IMAGE PATTERN OF VARIATIONS IN ELECTRICAL CONDUCTIVITY IS PRODUCED IN A PHOTOCONDUCTIVE LAYER, THE STEPS OF ELECTRYLYTICALLY CATHODICALLY DEPOSITING A SPONGY IMAGE, APPLYING A GELATIN HARDENING AGENT TO SAID IMAGE TO BE ABSORBED THEREBY AND PLACING IN CONTACT WITH THE IMAGE A 